Two core switches are linked by a port channel (built with two physical links).
Several access switches are in turn dual-linked to these core switches. STP is configured and operating on all vlans.
I added a vlan ("switchport trunk allowed vlan add xx") to one of the physical endpoints of the portchannel instead of doing this on the portchannel interface itself.
As soon as I executed the command, a storm of duplicated mac addresses started to be logged and the CPU of both core switches skyrocketed close to 100%. Many MAC addresses seemed to be coming into each core switch from different links at the same time, so a STP loop was generated as the result of my action.
I was explained that I should have added the new vlan to the portchannel, because this command would have been automatically propagated to the physical links that are part of the channel.
My question is: Â¿is there a relationship between the command I entered and the (supposedly STP) loop I observed on these switches?
Any help will be greatly appreciated.